Moesin controls cortex organization and contractility throughout mitosis. (A) Proportion of mitotic cells present in the respective steps of cell division, as deduced from fixed sample examination. Inactivation of moesin led to an increased proportion of cells in metaphase over the total number of mitotic cells. This increased proportion of metaphase indicates a delayed anaphase onset, which is also apparent in most time lapses. (B) Time-lapse frames of histone H2B–GFP (blue) S2 cells in control (top) or after moesin depletion (bottom) showing abnormal cortical protrusions (arrows) from pro/metaphase to ana/telophase. In this peculiar case, there was an eventual regression of the cytokinesis furrow even though the metaphase duration was not affected. cf, cleavage furrow. (C) F-actin (red) accumulated in ectopic cell bulges (arrows) in moesin-depleted cells throughout mitosis. DNA is in blue. (D) Consequences of moesin depletion on the distribution of myosin II heavy chain in metaphase and telophase. Myosin II heavy chain was irregularly localized (arrows) in the absence of moesin. (E) Actomyosin contractions were monitored in S2 cells expressing Sqh-GFP. Moesin depletion led to the chaotic distribution of contractile myosin (arrows) and contractions. (F) Consequences of moesin depletion on the distribution of active RhoA. RhoA was irregularly localized (arrows) in the absence of moesin. Bars, 10 μm.